Telescoping joint assembly and a method for making the same

ABSTRACT

A telescoping joint assembly and a method for making a telescope joint assembly  10.  The joint assembly  10  has a pair of members  12, 14  which are telescopically engaged. Assembly  10  further includes a resinous, plastic and/or polymer material  16  which shrinkably coats or lines the inner shaft  12  after the inner shaft  12  is heated and exposed to a substantially inert gas, thereby providing a relatively durable and substantially “low friction” bearing or surface 18 which is effective to promote and/or assist the telescopic sliding motion between the members  12, 14.

FIELD OF THE INVENTION

[0001] This invention relates to a joint assembly and a method formaking a joint assembly, and more particularly to a telescoping jointassembly and a method for making a telescoping joint assembly having apair of members which telescopingly cooperate to form a relatively tightand reliable joint.

BACKGROUND OF THE INVENTION

[0002] Automotive vehicles and other types of assemblies often utilizetelescoping type joints and/or joint assemblies to operatively coupleselectively rotatable shafts or members in a manner which allows torqueor rotational energy to be communicated and/or transmitted by andbetween the coupled members, while concomitantly allowing the coupledmembers to independently move axially with respect to each other (e.g.,to selectively move “toward and away” from each other).

[0003] For example and without limitation, a vehicle steering system orassembly generally includes a steering shaft or column and a telescopingintermediate shaft which is coupled to and transfers torque between asteering column and a steering gear assembly. Particularly, therotational energy of the steering column is transferred through thetelescoping intermediate shaft to the gear assembly and the wheelsuspension assembly, thereby allowing the vehicle to be selectivelysteered.

[0004] Typically, the intermediate shaft comprises and/or includes aninner shaft or member and an outer shaft or member which movably andselectively receives and/or “mates” with the inner shaft or member andwhich cooperates with the inner member to allow the steering column andgear shaft to be “axially compliant” (i.e., to selectively andindependently move “toward and away” from each other).

[0005] In order to substantially reduce friction and improve theperformance, compliance, and efficiency of this intermediate shaftand/or steering shaft assembly (as well as other types of jointassemblies), the inner member is typically coated or lined with a resin,rubber or polymer material, or contains a bearing assembly. Thetelescoping intermediate shaft compensates for the relative movementbetween the vehicle body and vehicle frame which occurs as the car isdriven and allows at least one of the coupled members, such as thesteering column, to substantially and desirably “collapse” in the eventof a collision or accident, thereby substantially reducing theprobability of injury to the driver. The telescoping shaft may furtherallow the steering column to be adjusted by the driver in an axial ortelescopic manner.

[0006] Although this intermediate shaft, as well as other substantiallysimilar types of prior joint assemblies, effectively transmit torquebetween a pair of coupled members or shafts while concomitantly allowingthe coupled members to be axially compliant, they suffer from somedrawbacks.

[0007] For example and without limitation, these prior joint assembliesare typically relatively loose fitting and do not have a relativelyprecise fit or “correspondence” between the telescoping members and/orbetween one or more of the telescoping members and the liner or bearingassembly. Particularly, because the members and the liner/bearingassembly are each formed by separate and independent processes, themanufacturing “tolerance” associated with each of the members and theliner/bearing assembly are additively accumulated or “stacked”, therebyresulting in a relatively “loose” overall tolerance and a relativelyimprecise or relatively loose fit. As a result, these prior telescopingjoint assemblies suffer from undesirable “slop”, “lash”, vibration,frictional loss, and/or “frictional lock-up”, which require relativelycostly and complicated modifications.

[0008] Particularly, these undesirable attributes hinder and/orundesirably diminish the sliding engagement between the telescopingmembers, resulting in an inefficient transmission of torque orrotational energy while concomitantly creating excessive wear andfatigue to and of the telescoping members, thereby causing failureand/or diminished performance (e.g., undesirably allowing vibrationalforces and/or other movements/forces to be readily transferred betweenthe coupled components and/or members, such as between the wheelsuspension assembly and the steering column).

[0009] Efforts to improve these relatively loose joints typicallyinclude but are not limited to relatively costly sizing, adjusting, ormachining of the respective shafts. Furthermore, in order to obtain amore precise tolerance or fit between the inner and outer members, themembers must typically undergo relatively complex and undesirablemachining processes after they have been formed and/or after a lininghas been applied to the inner and/or outer member. This“post-fabrication” machining undesirably increases the expense, time,and difficulty of the manufacturing process.

[0010] There is therefore a need to provide a telescoping joint assemblyfor coupling two members or shafts which overcomes at least some of thevarious and previously delineated drawbacks of prior couplingassemblies; which allows torque and rotational energy to be relativelyefficiently transmitted between the two coupled members or shafts, whileconcomitantly allowing each of the members or shafts to be axiallycompliant; which provides for a substantially “tight” fit between thetelescoping members; which substantially eliminates and/or reduces“slop”, lash, frictional loss, and/or “frictional lock-up”; and whichsubstantially eliminates the need for post-fabrication “machining” ofthe telescoping members.

SUMMARY OF THE INVENTION

[0011] It is a first object of the invention to provide a telescopingjoint assembly and a method for making a telescoping joint assemblywhich overcomes some or all of the previously delineated drawbacks ofprior telescoping joint assemblies.

[0012] It is a second object of the invention to provide a telescopingjoint assembly which selectively allows torque and/or rotational energyto be transmitted and/or communicated between two telescoping members,while concomitantly allowing the telescoping members to selectively,independently, and reciprocally move toward and away from each other.

[0013] It is a third object of the present invention to provide atelescoping joint assembly which provides for substantially “tight” orprecise dimensional fit or correspondence between two operativelyassembled telescoping members.

[0014] It is a fourth object of the present invention to provide atelescoping joint assembly which substantially eliminates and/or reduces“slop”, “lash”, frictional losses and/or “frictional lock-up”, and whichsubstantially eliminates and/or reduces the amount of vibrational forcestransferred between the coupled members.

[0015] According to a first aspect of the present invention, atelescoping joint assembly is provided. The telescoping joint assemblyincludes a first member having an inner cavity; a second member which isselectively and movably disposed within the cavity and which cooperateswith the first member to form a gap; a certain amount of a thermoplasticmaterial which is disposed within the gap and which selectively shrinksand solidifies, thereby bonding to the second member and allowing thesecond member to be slidably disposed within the cavity.

[0016] According to a second aspect of the present invention a methodfor making a telescoping joint assembly is provided. The method includesthe steps of providing a first member having a cavity of a first shape;providing a second member adapted to be inserted within the cavity;placing an amount of thermoplastic material within the cavity; heatingthe cavity effective to liquefy the thermoplastic material; heating thesecond member; inserting the heated second member within the cavity,effective to cause the thermoplastic material to be distributed withinthe cavity and around the second member; cooling the first membereffective to solidify the material, thereby bonding the material ontothe second member and creating a telescoping joint assembly.

[0017] These and other objects, aspects, features, and advantages of thepresent invention will become apparent from a consideration of thefollowing specification and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a perspective unassembled view of a joint assembly whichis made in accordance with the teachings of the preferred embodiment ofthe invention;

[0019]FIG. 2 is a cross sectional view of the joint assembly which isshown in FIG. 1 and which is taken along view line 2-2;

[0020]FIG. 3 is an enlarged cross sectional view of the joint assemblywhich is shown in FIG. 1, which is taken along the view line 2-2, andwhich is shown in a partially fabricated state;

[0021]FIG. 4 is an enlarged cross sectional view of the joint assemblywhich is shown in FIG. 1, which is taken along the view line 2-2, andwhich is shown in a fabricated state;

[0022]FIG. 5 is a partial cross sectional view of the joint assemblywhich is shown in FIG. 1, which is taken along the view line 2-2, andwhich is shown in a fabricated and unassembled state; and

[0023]FIG. 6 is an enlarged cross sectional view of the joint assemblywhich is shown in FIG. 4, which is taken along view line 6-6, and whichis shown in an assembled state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

[0024] Referring now to FIGS. 1-6, there is shown a telescoping jointassembly 10, which is made in accordance with the teachings of thepreferred embodiment of the invention. The joint assembly 10 includes aninner shaft or member 12 which is adapted to be selectively, operativelyand slidably inserted into and to selectively engage a generally hollowor tubular outer shaft or member 14. Assembly 10 further includes aresinous, plastic or polymer material 16 which is inserted into member14 and which, as explained more fully below, coats or lines the innershaft 12, thereby providing a relatively durable and low frictionbearing or surface 18 which is effective to promote and/or assist thetelescopic sliding motion between the members 12, 14 in manner which ismore fully delineated below.

[0025] In the preferred embodiment of the invention, member 12 includesan outer surface 20, which is coated, lined or covered by material 16,as best shown in FIGS. 4-6. Particularly, as best shown in FIG. 6,surface 20 has a generally oblong cross sectional shape which iscooperatively formed by two opposing substantially flat surface portions22, 24 which are integrally formed with and which terminate upon opposedgenerally convex and semi-circular surface portions 26, 28. Surface 20includes a knurled or raised projection, protuberance, or formation 30which protrudes and/or outwardly projects from surface 20 and which, asdescribed more fully and completely below, is adapted to selectivelyengage the solidified material 16, thereby securing the material tomember 12. In other alternate embodiments, projection 30 comprises oneor more indentations, grooves or openings disposed upon and/or withinsurface 20 and which are each effective to “hold” or secure at least aportion of the solidified material 16 onto surface 20, thereby securingat least a portion of the solidified material 16 to member 12.

[0026] Member 14 further includes and/or forms a cavity 34 which isbounded by and/or is defined by an inner surface 32. Cavity 34 has agenerally oblong cross sectional shape which is substantially andintegrally formed by two opposing substantially flat surface portions36, 38 which are integrally formed with and which terminate upon twoopposed, concave, and semi-circular surface portions 40, 42. As shown,surface 20 and surface 32 have substantially similar and correspondingshapes with the exception that surface 32 is relatively larger in sizeand/or surface area than surface 20. Hence, when inner member 12 isinserted into cavity 34, a substantially uniform distance or gap 44 isformed between surface 20 and surface 32. In one non-limitingembodiment, the distance or gap 44 between surfaces 20 and 32 (i.e.,between each of surfaces 22-28 and the respective and opposing surfaces36-42) is substantially uniform. In alternate embodiments, surfaces 20and 32 each include a plurality of conventional and corresponding“splines” which are circumferentially formed upon the respectivesurfaces 20, 32 and which are adapted to selectively and cooperativelyintermesh.

[0027] As best shown in FIGS. 4 through 6, material 16 substantially anduniformly coats or lines the portion of member 12 which telescopicallypenetrates cavity 34 and/or engages member 14. Material 16 is resinousand/or polymeric in nature and, in one non-limiting embodiment of theinvention, comprises thermoplastic material such as acetal, 6:6 nylonmaterial. As discussed more fully and completely below, once assembly 10is fully assembled and/or formed, material 16 substantially anduniformly occupies or resides within gap 44. The outer surface 18 of thesolidified material 16 is substantially similar in shape to surfaces 20and 32 with the exception that surface 18 is relatively larger in sizeand/or has a relatively larger surface area than does surface 20 and isrelatively smaller in size and/or has a relatively smaller surface areathan does surface 32. Hence, a substantially uniform distance or gap 48is formed between surfaces 18 and 32. The gap 48 between surfaces 18 and32 is relatively small, thereby providing a considerably precise fitbetween the engaging portions of members 12 and 14. In one non-limitingembodiment, the distance or gap 48 between surfaces 18 and 32 issubstantially uniform and equal to about 0.03 inches. This relativelyminute gap 48 substantially prevents members 12 and 14 fromindependently rotating with respect to each other, thereby allowingjoint assembly 10 to effectively transmit torque between the selectivelycoupled members 12 and 14. This relatively small distance 48 and precise“dimensional fit” between material 16 and outer member 14 furthersubstantially eliminates “lash” and vibration and improves the overalloperational “smoothness” of assembly 10.

[0028] This relatively minute gap or distance 48 is created through thenovel method of assembling and/or fabricating joint assembly 10. As bestshown in FIGS. 1-5, assembly 10 is assembled and/or fabricated asfollows.

[0029] Member 14 is initially inserted into a fixture 56, which securesmember 14 in a substantially “upright” position. Cavity 34 is thenfilled or “flooded” with an inert gas (e.g., the air and/or other gassesresident within cavity 34 are forcibly and intentionally replaced withan inert gas). In another non-limiting embodiment, member 12 and 14 mayalso be immersed within the inert gas or the gas filled cavity 34. Inthe preferred embodiment of the invention the inert gas comprises argongas, although other inert gasses may be utilized. The presence of theinert gas within cavity 34 substantially prevents the metal of members12, 14 from oxidizing, and further substantially prevents degradation ofmaterial 16. In other alternate embodiments, the entire assembly and/orfabrication process is performed within an inert gas environment,thereby causing substantially the entire surface 32 of member 12 andsurface 20 of member 14 to be selectively exposed to the inert gas.Members 12 and 14 are then each respectively heated by the use ofconventional heat induction coils 50, 52. Particularly, members 12, 14are heated until they reach a predetermined temperature which issubstantially greater than the melting point of material 16.

[0030] After cavity 34 is filled with the inert gas and the members 12,14 are heated, a predetermined amount of material 16 is placed withincavity 34, as best shown in FIG. 2. In the preferred embodiment of theinvention, material 16 is melted or liquefied prior to its insertionwithin cavity 34. However, it should be appreciated that material 16 maybe placed within cavity 34 in a substantial “solid form” or “solidstate” and subsequently melted within the cavity 34 by the use of heatinduction from coil 52 and member 14. Member 12 is then graduallyinserted into cavity 34.

[0031] Since the temperature of members 12, 14 is above the meltingpoint of the material 16, as member 12 is inserted into cavity 34,material 16 remains in its liquid or molten state and is displacedaround the outer surface of member 12 as the member 12 is inserted intocavity 34. Particularly, as shown best in FIG. 3, when member 12 isfully inserted into cavity 34, material 16 substantially fills the gap44 formed between the outer surface 20 of member 12 and the innersurface 32 of member 14.

[0032] Once member 12 has been fully inserted into cavity 34, theliquefied material 16 is substantially and evenly distributed betweensurfaces 20 and 32. The heat provided by coil 52 is then selectivelyremoved or “lowered”, thereby allowing heat to dissipate from assembly10 and reducing the temperature of members 12, 14 and material 16. Asthe temperature of material 16 decreases, the material 16 begins tosolidify and/or harden. The solidification of material 16 causes thematerial 16 to shrink or decrease in size by a predetermined andrelatively highly predictable amount, and further causes the material 16to bond or attach to member 12. As the material 16 solidifies, therelatively small, uniform and precise gap 48 is formed, therebyproviding a highly precise mating between members 12 and 14. It shouldbe appreciated that by casting material 16 within the engaged members12, 14, the gap 48 is determined solely by the relatively highlypredictable, uniform and controlled shrinkage of material 16. As such,the present invention substantially avoids the “tolerance stacking”associated with prior art telescoping joint assemblies.

[0033] Once material 16 has solidified, projection 30 secures material16 to member 12. After material 16 has solidified and cooled, member 12is removed from cavity 34 and a conventional and commercially availablelubricant, such as grease or oil, may be selectively applied to theouter surface 18 of solidified material 16 and/or to the inner surface32 of member 14 in order to reduce sliding type friction between theengaged members 12, 14.

[0034] In one non-limiting embodiment, joint assembly 10 replaces thetraditional and previously delineated telescoping intermediate and/orsteering shaft which is resident within a vehicle steering assembly. Inthis configuration, end 54 of member 12 is operatively attached to thevehicle steering column in a conventional manner and end 56 of member 14is operatively attached to the vehicle gear shaft or gearbox in aconventional manner. In this manner, the selective torque or rotationalenergy, which is generated by the steering column, is transferred and/orcommunicated through assembly 10 to the gear shaft in a manner whichallows the gear shaft to concomitantly and axially articulate toward andaway from the steering column.

[0035] Particularly, as forces and/or vibrations are imparted uponassembly 10, by way of the typical wheel suspension assembly, member 12selectively, telescopically, and movably penetrates member 14 and cavity34, thereby substantially eliminating the relative torsional motionbetween member 12 and member 14, and substantially preventing suchmovement, vibration, lash, or slop from being communicated to thesteering column. The axial movement provided by assembly 10 also allowsthe steering column to desirably “collapse” in the event of a collisionor accident and/or to be selectively adjusted in a telescoping manner ormotion.

[0036] Importantly, the relatively tightly fitted telescoping members 12and 14 allow the steering column and the gear shaft to smoothly andconsistently articulate, with respect to each other, and substantiallyreduces and/or eliminates “slop”, “lash”, vibration, frictional lossesand/or “frictional lock-up” associated with the relatively “loose”tolerances of prior telescoping intermediate shafts and/or steeringshaft assemblies.

[0037] It should be appreciated that the assembly 10 may be selectivelyused within various other applications requiring the coupling of twoaxially compliant members and the transmission or resistance of torqueand/or rotational energy by and between these coupled members. It shouldfurther be appreciated that while a pair of shaft type members 12, 14are shown, assembly 10, as well as the various other coupling assembliesdescribed herein, is adapted to couple other types, shapes, and/or formsor members and to provide the described coupling benefits and/orattributes to these other coupling arrangements.

[0038] It is understood that the invention is not limited by the exactconstruction or method illustrated and described above but that variouschanges and/or modifications may be made without departing from thespirit and/or the scope of Applicants' inventions.

What is claimed is: 1) A telescoping joint assembly comprising: a firstmember having an inner cavity; a second member which is selectively andmovably disposed within the cavity and which cooperates with the firstmember to form a gap; and a certain amount of thermoplastic materialwhich is disposed within the gap and which selectively shrinks andsolidifies, thereby bonding to the second member and allowing the secondmember to be slidably disposed within the cavity. 2) The telescopingjoint assembly of claim 1 wherein said cavity has an oblong shape. 3)The telescoping joint assembly of claim 1 wherein said formationcomprises a knurled portion. 4) The telescoping joint assembly of claim1 wherein said formation comprises an indentation. 5) The telescopingjoint assembly of claim 1 wherein said material comprises a polymericmaterial. 6) The telescoping joint assembly of claim 5 wherein saidpolymeric material comprises 6:6 nylon, acetal, thermoplastic. 7) Atelescoping joint comprising: a first member having an inner cavity witha concave surface; a second member having a convex surface which isdisposed within said cavity and which is separated from said concavesurface by a substantially uniform gap; and an amount of a thermoplasticmaterial disposed within said gap, said material solidifying in responseto a decrease in temperature, said solidification of said materialeffective to bond said material to said convex surface and to shrinksaid material by a predetermined amount, thereby allowing said secondmember to be slidably movable within said cavity. 8) The telescopingjoint assembly of claim 7 wherein said convex surface includes aprotuberance effective to further bond said material to said convexsurface. 9) The telescoping joint assembly of claim 7 wherein saidconvex surface includes an indentation effective to further bond saidmaterial to said convex surface. 10) The telescoping joint assembly ofclaim 7 wherein said thermoplastic material comprises 6:6 nylon, acetalthermoplastic. 11) The telescoping joint assembly of claim 7 whereinsaid first member and said second member concave surface are each oblongin shape. 12) A method for manufacturing a telescoping joint assembly,said method comprising the steps of: providing a first member having acavity of a first shape; providing a second member; heating said firstmember; placing an amount of liquefied thermosetting material withinsaid cavity; heating said second member; inserting said heated secondmember within said cavity effective to cause said liquefiedthermosetting material to be distributed within said cavity and aroundsaid second member; and cooling said first member effective to solidifysaid material and to shrink said material, thereby bonding said materialonto said second member. 13) The method of claim 12 further comprisingthe step of disposing a knurl upon said second member, said knurl beingeffective to secure said solidified material upon said second member.14) The method of claim 12 further comprising the step of creating anindentation within said second member, said indentation being effectiveto secure said solidified material upon said second member. 15) Themethod of claim 12 further comprising the step of placing said firstmember, said second member, and said material within an environmentcontaining inert gas. 16) The method of claim 12 further comprising thestep of applying a lubricant to said solidified material. 17) The methodof claim 12 further comprising the step of filling said cavity with aninert gas. 18) The method of claim 12 wherein said inert gas comprisesargon.